1. Field of the Invention
The present invention relates to underpinning pile assemblies. More particularly, the present invention the relates to underpinning pile assemblies in which friction on the exterior surface of the underpinning piles is reduced during the installation process. Additionally, the present invention relates to underpinning pile assemblies formed of a plurality of steel pipes arranged in stacked relation.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Many structures, such as residential homes and low-rise buildings, are constructed on foundations that are not in direct contact with a stable load-bearing underground stratum. These foundations are typically concrete slabs upon which a foundation wall rests. The footing is generally wider than the foundation wall in order to distribute the structure's weight over a greater surface area of load-bearing earth. As a result, the stability of the structure depends upon the stability of the earth below the foundation. Over time, the stability of the underlying soil may change for many reasons. When the stability of the support earth changes, the foundation may move or settle. This settling of the foundation can cause structural damage to the structure upon the foundation.
One common device and method to correct foundation settling is the employing of hydraulic jacks in conjunction with piers so as to lift the foundation. Piers, also known as piles or pilings, are driven into the ground by hydraulic mechanisms until the pier reaches bedrock or until the pier's frictional resistance equals the compression weight of the structure. Once the piers are secured in a stable underground stratum or several stable underground strata, further lifting by the hydraulic jacks raises the level of the foundation. When the foundation is raised to the desired level, the piers are permanently secured to the foundation. The hydraulic jacks are then removed.
Steel piers are well known and exist in many varieties. One common type of a pier is a straight steel pier that is driven down until it reaches bedrock or stable soil weight-bearing layers. These straight steel piers are rammed straight down into the ground.
During the installation of such steel piers in heavy clay soil, there is strong frictional contact between the heavy clay soils and the exterior surface of the steel pipes that are used for such steel piers. Eventually, the frictional force which contacts the exterior surface of these steel pipes becomes so great that further and deeper installation becomes difficult or impossible. Additional hydraulic power may be necessary so as to install such steel piers to the desired depth. Additionally, the ballast that is used so as to counteract the force of the hydraulic jack may be insufficient to achieve the forces necessary so as to effectively install the steel piers. Under such circumstances, the steel piers may not reach their desired depth. Additionally, this strong friction between the exterior surface of the steel pipe can significantly increase the amount of time devoted to the installation procedure. As such, a need has developed whereby the steel piers can be installed by reducing the friction force between the heavy clay soils and the exterior surface of the steel piers.
During the installation of such steel piers, it is desirable to power wash through the interior of the steel pipe. This power washing includes injecting water under great pressures through the interior of the steel pipes so that water is released at the bottom of the pier assembly. This will cause any soils below the end of the driving segment of the steel piers to fluidize such that the driven pier can move easily through the soil. Additionally, materials beneath the steel piers can be effectively removed through this power washing procedure. As such, a need has developed so as to create a low friction installation of such steel piers while, at the same time, maintaining the benefits of such power washing procedures.
In the past, a variety of patents have issued relating to the installation of such piles or piers. For example, U.S. Pat. No. 4,673,315, issued on Jun. 16, 1987 to Shaw et al., describes an apparatus for raising and supporting a building. The lifting assembly is inserted underneath the foundation or slab and is adapted to receive a pipe assembly. A clamping assembly is provided for engaging a portion of the pipe assembly extending above the lifting assembly. A hydraulic system extends between the lifting assembly and the clamping assembly for sequentially lowering the pipe assembly into the earth such that, when it encounters resistance, the foundation or slab is supported and can be raised to a predetermined level.
U.S. Pat. No. 4,678,373, issued on Jul. 7, 1987 to Langenbach, Jr., discloses an apparatus for shoring a structure. This apparatus includes a support bracket engageable with the foundation, a pile adapted to be driven down into the ground adjacent the bracket, and at least one footing structure on the outside of the pile extending circumferentially of the pile in a plane generally at right angles to the central longitudinal axis of the pile. The footing structure has an outer diameter greater than the outer diameter of the pile for engagement with the soil as the pile is driven down so as to increase the load-bearing capacity of the pile.
U.S. Pat. No. 5,336,021, issued on Aug. 9, 1994 to P. R. Freeman, III, shows a system for underpinning a building. A pier driving assembly is disclosed which supports the foundation under compression forces. The pier driving assembly includes a pier driving bracket which drives the pier pipes into the ground, a pier head which is placed on the pier pipe after the pipe has been driven to bedrock and the pier driving bracket assembly has been removed, and a loading bracket which gives the final lift to the foundation to make it level.
U.S. Pat. No. 6,179,526, issued on Jan. 30, 2001 to Knight et al., provides a method for forming a pile isolation void which includes forming a foundation pile having an enlarged cross-section within a specific localized section and driving the foundation pile a desired distance into the earth so as to form a pile isolation void directly above the enlarged cross-section. The enlarged cross-section can be located at the bottom of the foundation pile or along the length of the foundation pile. The pile isolation void is an annular void extending around the foundation pile above the enlarged cross-section. This pile isolation void can be filled with a material, such as liquid, gel, or a solid material different than the material of the pile or of the earth. The enlarged cross-section can be a collar placed upon the foundation pile, or integrally formed with the foundation pile.
U.S. Pat. No. 7,044,686, issued on May 16, 2006 to D. May, provides an apparatus and method for supporting a structure with a pier. The pier assembly is provided with a rotatable shelf so as to secure a screw jack assembly under a footing of a foundation.
U.S. Pat. No. 7,195,426, issued on Mar. 27, 2007 to D. May, teaches a structural pier and method for installing the structural pier. The pier includes a pier shaft, a bracket mounted to a top end of the pier shaft that supports the weight of the foundation, and a pair of braces that extend laterally from the pier shaft and mount to the foundation.
U.S. Pat. No. 7,857,549, issued on Dec. 28, 2010 to the present inventor, discloses an underpinning pile assembly for supporting a structure upon the earth. This underpinning pile assembly has at least one steel pipe, at least one concrete pile segment positioned above the steel pipe, and a transition member interposed between the steel pipe and the concrete pile such that the load of the concrete pile is supported by the steel pipe. The steel pipe includes a plurality of steel pipe segments extending in end-to-end relationship in generally vertical alignment. A key member is received in slots formed in the respective ends of the first and second segments. The plurality of concrete pile segments includes a strand affixed in holes formed through the plurality of concrete pile segments.
U.S. Pat. No. 8,272,810, issued on Sep. 25, 2012 to Dimitrijevic et al., shows pilings for foundation underpinning. A pile segment includes a head, a trunk extending from the head, and a throughbore passing axially through the head and the trunk. The throughbore has a longitudinal centerline. The area of a cross-section through the head and normal to the centerline is greater than the area of a cross-section through the trunk and normal to the centerline.
It is an object of the present invention to provide an underpinning pile assembly which serves to reduce friction between the surfaces of the underpinning pile assembly and the earth during the driving of the pile.
It is another object of the present invention to provide an underpinning pile assembly which facilitates the ability to drive pile in heavy clay soils.
It is still another object of the present invention to provide an underpinning pile assembly that offers better penetration when there is a lack of sufficient ballast.
It is still another object of the present invention to provide an underpinning pile assembly which facilitates the use of power washing through the interior of the steel pipe of the underpinning pile assembly.
It is still a further object of the present invention to provide an underpinning pile assembly that can be easily assembled at the word site.
It is still a further object of the present invention to provide an underpinning pile assembly which reduce the time required for the installation of the underpinning pile assembly.
It is a further object of the present invention to provide an underpinning pile assembly which minimizes the amount of hydraulic force required to reach the desired depth.
It is still another object of the present invention to provide an underpinning pile assembly which reduces the amount of time required to install the pile assembly.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.